CN1628446B - Method and sytem for receiving multi-carrier signal - Google Patents

Abstract

Method and system for reducing impulsive burst noise in less delayed reception in pilot based OFDM systems, especially using DVB-T standard such as Digital Video Broadcasting (DVB) is provided. The method contains following steps: recognition of the impulse position and possibly length in the time domain symbol, blanking of those samples of the symbol where significant amount of impulse noise is present, calculating the first estimate of the received signal from the blanked symbol, derving correction values for the carrier estimates by applying prior information (pilot carriers), and the corrected estimate of the received symbol is derived by subtracting the correction values of step from the first estimate of carriers derived in step. The method and arrangement allow correction of fairlylong bursts of impulse noise with minor degradation only. The complexity of the scheme and the additional energy consumption are fairly low. The method provides considerably more effective more simpleand less delay in broadcast data reception than previously known solutions in interfered multi-carrier signal reception.

Description

Receive the method and system of multi-carrier signal

Technical field

The present invention relates to system and method by the communication link distribute data.

Background technology

Radio broadcasting has the almost history in a century.Even TV, history also can be traced back to nineteen thirties.At All Around The World, broadcasting is successfully given the audient entertainment and information band.

The up-to-date measure of broadcasting is the digitlization of radio broadcasting and TV.Digital radio broadcasting does not obtain too many market approval.But many people wish that digital TV will bring new benefit of consumer and service, thereby, for broadcast industry produces new financial resources.But the basic principle of TV service itself does not have too many change.On the contrary, even become numeral, TV was still as in the past.

In the second half section of nineteen nineties, the internet is universal day by day.In short change and propagate in ardent period, a whole lot of new service and content become and are applicable to the consumer.This section introduced ecommerce period, ISP (ISP), portal website, eyeball recreation .com company, even New Economy.The development of access technology (for example ADSL) and coding techniques (for example MPEG-4 fluidisation) direction makes it possible to provide abundant media content by the internet to family, such as video content.Break through although these technology and market have occurred, because its " freely " property, medium publishing house still be unwilling to issue their content by the internet.Although very universal, the role of traditional media as main advertising platform can not be challenged in the internet.

In broadcasting, observe impulse disturbances, cause the difficulty of broadcast reception aspect.This interference may be by from vehicle or various household electrical appliance, and for example the pilot spark of hair-dryer, vacuum cleaner, drilling machine etc. produces.The inexpensive designs of these instruments does not have enough interference usually and suppresses.In addition for the same reason, when opening or closing, can produce pulse or even pulse train with any device that power line is connected.These devices can be electric heater units, controllable silicon dimmer, fluorescent lamp, refrigerator etc.Especially in the indoor reception that utilizes simple omnidirectional antenna, must consider this point.The field intensity of broadcast singal, especially for being positioned at indoor mancarried device, may be very low, and by further weakening of multipath reception.Receive for fixing, the not enough cable shield that indoor signal distributes usually reduces the benefit of roof antenna, makes signal receive paired pulses and disturbs responsive.

Attempt to solve a kind of method of impulsive noise based on the amplitude limit pulse train.After the amplitude limit, sample is endowed the value corresponding with the clip level amplitude (and keeping phase place).Perhaps the value behind the amplitude limit can be assigned 0, because known these samples under any circumstance all are insecure.In these areas, this method example is patent announcement EP 1043874A2 (being contained in this as a reference).In this bulletin, detect in the time domain, surpass the signal level of specific clip level, replace these samples with 0 subsequently.But this method is not touched ruined, but the sample that is not limited, and this causes relatively poor signal-interference ratio, if all the more so when especially burst power is higher.In addition, amplitude limit method does not detect, and touches impulse level, this means that their ability is restricted.In addition, only make signal blanking meeting make signal to noise ratio relatively poor.

The another kind of known method of attempting to solve impulsive noise is to make known ruined all samples, for example belongs to all sample blankings in disturbing pulse cycle.The knowledge of pulse position and duration can be based on for example to surpassing the supervision of specific clip level.At publication, Sliskovic, M:Signalprocessing algorithm for OFDM channel with impulse noise, Electronics, Circuits and Systems, 2000, ICECS 2000,7 ^ThIEEE InternationalConference, Volume:1,2000, so a kind of method is proposed among the page:222-225vol.1 (being contained in this as a reference).But this method is too simple, because all pulse trains that interference suspicion arranged are all by blanking.Amended pickup electrode is different from primary signal, because all data values in disturbing all are empty, does not have any correspondence between original value.Thereby, only make invalidating signal can make signal to noise ratio relatively poor.Better for the performance that makes blanking method, can attempt finding the solution the equation of the sample that provides the primary signal that has been eliminated.If detect noise burst, and the time corresponding sample is by blanking, can use so in theory that (in boundary belt) should not exist the information of any signal to recover original back FFT value on unloaded ripple.In the IEEE publication of quoting, this method has been described.Unfortunately, the method for describing in this list of references need be found the solution the complication system equation, and this had not only bothered but also heavy (descriptor matrix is inverted, and the dimension of matrix is hundreds of or even thousands of).This complexity is difficult to find the solution.In addition in system's (for example ofdm system), only depend on portions of the spectrum in the boundary belt and prove poor efficiency with the thousands of carrier wave that receives by noisy channel.Can not find the solution the sample that lacks reliably.In addition, receiver can not be carried out required complicated in theory calculating.In addition, be subject to noise about the information of boundary belt and damage, answer is inaccurate.So, need be used for the quite simply approximate solution of estimator, this solution can postpone not too to determine estimator under the serious situation.

Thereby, needing the less reception of a kind of better simply delay, it can resist the interference of higher aquatic products, impulse disturbances for example, and can improve the Data Receiving quality.

Summary of the invention

Invention now is a kind of resists the method and apparatus that passes through the impulse disturbances in the multi-carrier signal that communication link transmits of reception.

According to a first aspect of the invention, a kind of method that receives multi-carrier signal is provided, described method comprises the steps: to detect the existence of at least one impulse disturbances in the described signal, under the situation that has a large amount of impulsive noises that cause by at least one impulse disturbances, the blanking sample, thereby obtain to have the signal of blanking, determine to have the estimator of the signal of blanking, determine the carrier wave corrected value, described carrier wave corrected value to be comparing with Given information, the departing from of some carrier value, and described blanking is the basis, and influence estimator, thereby obtain the reproduction of desired signal with the carrier wave corrected value.

According to a second aspect of the invention, a kind of receiver that receives multi-carrier signal is provided, described receiver comprises: first circuit that detects the existence of at least one impulse disturbances in the described signal, under the situation that has a large amount of impulsive noises that cause by at least one impulse disturbances, the blanking sample, thereby obtain to have the signal of blanking, and determine to have the second circuit of estimator of the signal of blanking, determine the tertiary circuit of carrier wave corrected value, described carrier wave corrected value to be comparing with Given information, the departing from of some carrier value, and described blanking is the basis, influence estimator with usefulness carrier wave corrected value, thereby obtain the 4th circuit of the reproduction of desired signal.

According to a third aspect of the invention we, a kind of system that receives multi-carrier signal is provided, described system comprises: the device that detects the existence of at least one impulse disturbances in the described signal, under the situation that has a large amount of impulsive noises that cause by at least one impulse disturbances, the blanking sample, thereby acquisition has the device of the signal of blanking, determine to have the device of estimator of the signal of blanking, determine the device of carrier wave corrected value, described carrier wave corrected value to be comparing with Given information, the departing from of some carrier value, and described blanking is the basis, influence estimator with usefulness carrier wave corrected value, thereby obtain the device of the reproduction of desired signal.

According to a forth aspect of the invention, a kind of computer program that comprises instruction repertorie is provided, described instruction repertorie can be carried out by computing system, be used to handle the reception of broadcasting multi-carrier signal, described computer program comprises: make system detect the computer program code of the existence of at least one impulse disturbances in the described signal, under the situation that has a large amount of impulsive noises that cause by at least one impulse disturbances, make system's blanking sample, thereby acquisition has the computer program code of the signal of blanking, make system determine to have the computer program code of estimator of the signal of blanking, make system determine the computer program code of carrier wave corrected value, described carrier wave corrected value is to compare with Given information, departing from of some carrier value, and described blanking is the basis, with make system influence estimator with the carrier wave corrected value, thereby the computer program code of the reproduction of acquisition desired signal.

Description of drawings

Below with reference to accompanying drawing, illustrate the present invention, wherein:

Fig. 1 represents an example of the generation that transmits among the DVB-T;

Fig. 2 represents to be applicable to the example and the pilot signal of the frame structure of one embodiment of the invention are how to be arranged in DVB-T's;

Fig. 3 represents to use the general architecture of system of the principle of embodiments of the invention;

Fig. 4 graphic extension is the example of time-domain signal according to an embodiment of the invention;

Fig. 5 is the functional-block diagram that receives multi-carrier signal, and wherein according to one embodiment of present invention, impulse disturbances is reduced in the Data Receiving of less delay;

Fig. 6 has described the method that receives the multichip carrier signal in a flowchart, and wherein according to one embodiment of present invention, impulse disturbances is reduced in the Data Receiving of less delay;

Fig. 7 represents to receive the receiver of multi-carrier signal, and wherein according to one embodiment of present invention, impulse disturbances is reduced in the Data Receiving of less delay;

Fig. 8 represents the example about the result of the ofdm signal with 2048 carrier waves, has proved according to another embodiment of the present invention that wherein the impulse disturbances of less delay reduces;

Fig. 9 has represented the example of the mean square deviation of from 0 to 500 carrier wave, wherein according to another embodiment of the present invention, has proved that the impulse disturbances of less delay reduces.

Embodiment

The preferred embodiments of the present invention provide in a kind of ofdm system based on pilot signal, reduce the method for the pulse train noise in the reception of less delay.

The certain methods of preferred embodiment comprises the steps: 1) identification in the time-domain symbol pulse position and may length, 2) there are those samples of the symbol of a large amount of impulsive noises in blanking, 3) according to the symbol of blanking, calculate first estimator of received signal, 4) by using information (for example pilot frequency carrier wave) formerly, obtain the corrected value of carrier estimation amount, 5) by first estimator from the carrier wave that step 3, obtains, deduct the corrected value of step 4, obtain the correction estimator of receiving symbol.Advantageously, this method and structure allows to proofread and correct quite long impulse noise burst string under less decay.The complexity of this scheme and extra energy consumption are quite low.Compare with the known solution of the multi-carrier signal reception aspect of being disturbed, this method provides more effective, simpler and postpones less broadcast data and receives.

The principle of some embodiments of the present invention based on according to observe with respect to the departing from of known pilot carrier value, obtain the least mean-square estimate amount of back Fourier (FFT) carrier wave corrected value.Proof and only the method for blanking signal compare this method even back detection mean square error (MSE) improved tens to 20 fens pages or leaves.When useful signal power reduced, the blanking of time domain samples must cause certain decay, but embodiments of the invention help avoid the many extra distortion that is caused by distorted signal.In other rational condition (rational carrier wave-noise ratio, not too fast decay) under, can tolerate in the 2k system blanking interval length about at least 500 samples (about 50 milliseconds) in the blanking interval length about at least 100 samples (about 10 milliseconds) and 8k system.In addition, can tolerate the blanking length that surpasses above-mentioned numeral, actual maximum length depends on the robustness of the transmission mode of selection, because residue MSE will increase pro rata with blanking interval length.

Advantageously, compare, can tolerate quite long impulse noise burst string with prior art.Proofread and correct the usefulness of the enough many situations of length available at interval.The elimination of bursts is insensitive to bursts intensity, and the bursts length of correction can be up to tens or even hundreds of samples.Though burst of pulses is corrected, to compare with glitch-free original transmitted signal, the deterioration of overall performance is quite little.If there is no impulsive noise, mis-behave is very little or even do not have so.This method is quite sane, estimates that interchannel noise can the rapid deterioration performance.This method is easy to be suitable for.Receiver detects pulse.Receiver can determine where pulse is positioned at.In a kind of simple method, even do not need pulse length.In fact the algorithm of using does not exist the difference that is caused by different impulsive noise situations.Required variation to existing chip design is very little, and can quite easily realize, the present invention is realized flexibly.Need some extra controls and some calculating.The type of calculating be present in compute classes so on the decoding chip like (channel estimating).So, can reuse some in those calculating, perhaps (at least) can repeat similar processing block in design.The required extra process time can be quite little.So, less delay takes place in the reception.In addition, only need forward calculation (not having feedback), this helps to keep the time budget of chip processing.It is quite reasonable to calculate required additional energy, can not cause any big obstacle to receiving system, and having only just needs impulsive noise to proofread and correct when having pulse.The present invention does not need inverse fast fourier transformed (IFFT), does not need the feedback (circuit) of any type yet, the opposite correction of directly carrying out estimated signal.So the present invention can realize that the broadcast data of less delayed receives, because the streaming character of broadcast transmitted, this is very desirable.In fact, only need a direct FFT.

Digital video broadcasting (DVB) provide high-bandwidth transmission channel, and wherein transmitting generally is broadcasting, multicast or clean culture.High-bandwidth transmission channel can provide various services to the user of this system.In order to concentrate on described service, the appropriate reception of the broadcast data of emission is essential.Digital video broadcast-terrestrial (DVB-T) is used Orthodoxy Frequency Division Multiplex (OFDM) in the signal emission, in an embodiment of the present invention, and advantageous applications DVB-T.On the other hand, the present invention also can be used in other ofdm system, for example, according to ground Integrated Services Digital Broadcasting (ISDB-T, the Nippon Standard that is used for received terrestrial digital broadcasting) transmission is because the system of these types provides and use known information, for example pilot value, and in signal bandwidth, also can have unloaded ripple or other constant carrier.

Digital broadcast transmission provides mass data information to acceptor device.Acceptor device should be able to fully receive the data of service.The essence of digital broadcast transmission is that transmission is to adopt broadcasting or multicast, at the streaming distribution of a plurality of receivers, perhaps at the point-to-point distribution of the clean culture of single receiver.The data allocations link that broadcasting transmits can be Radio Link, fixed link or wire link.For example, DVB-MHP (multimedia home platform) provides a plurality of data allocations links to receiver.Digital broadcasting transmission system can have the reciprocation with receiver, but described reciprocation is not a mandatory requirement.Have interactive system and can have wrong data by request repeat, but broadcast reception (have streaming and transmit essence) should be able to be tolerated the mistake in the data allocations.So the reception of Digital Transmission should be reliably, and tolerates for example impulse disturbances.In addition, the streaming of digital broadcasting essence proposes the restriction about the delay of broadcast data reception.Since less delay, structure and energy consumption, and the simplicity in the acceptor device is desirable.

Some embodiment of the signal of using among the present invention are based at standard EN 301 701V1.1.1 (2000-08) Digital Video Broadcasting (DVB); The method and system that proposes in the OFDM modulation of Digital Microwave terrestrial television, described standard is contained in this as a reference.

Some embodiments of the present invention are used the generation of transmission signals among the DVB-T.At publication EN300 744 V1.4.1 (2001-01) Digital Video Broadcasting (DVB); Proposed the solution of these types in the framing structure of digital terrestrial television, chnnel coding and the modulation, described publication is contained in this as a reference.Fig. 1 has represented an example of the generation that transmits among the DVB-T, has described this example in 4.1 chapters of EN 300 744.The operation of two kinds of patterns of definition: " 2K pattern " and " 8K pattern ".The small-sized Single Frequency Network (SFN) that " 2K pattern " is suitable for the operation of single transmit device and has limited reflector distance." 8K pattern " both can be used for the operation of single transmit device, can be used for small-sized and large-scale SFN network again.

The Given information of some embodiments of the present invention application distribution in transmission signals.Provided the solution of these types in the 4.5.3 chapter in publication EN 300 744.

Fig. 2 has represented the example of frame structure according to another embodiment of the present invention and pilot signal are how to be arranged in DVB-T's.In the scattered pilots unit of each symbol, transmit the reference information that from reference sequences, obtains.Always with " raising " energy level emission scattered pilots unit.Represented pilot tone interpolation pattern among Fig. 2.In Fig. 2, the pilot signal that the stain representative strengthens, the circle representative data information of inner white.Advantageously, the pilot signal of enhancing can be used as reference information formerly, is used for determining the corrected value of the estimator of the data value that destroyed by impulse disturbances.On the other hand, the interpolate value of the OFDM symbol of following or former pilot value can be used as Given information.In the present embodiment, acceptor device calculates interpolate value, and interpolate value can be used as reference information formerly.

Some embodiments of the present invention are used sample.The sample representative is every the time discrete value of reception (multicarrier) signal of basic duration acquisition.For example, in DVB-T, 7/64 microsecond of 8MHz channel.

The some embodiments of the present invention using symbol.In DVB, an OFDM symbol comprises N sample, and N represents the FFT scale here.Best, under the situation of unguarded interval, reproduce described symbol.

Some embodiments of the present invention can be used among the DVB-T, for example digital video broadcasting (DVB): the framing structure of digital terrestrial television, chnnel coding and modulation, ETSI EN 300 744.

The front has illustrated Fig. 3.Below, corresponding Reference numeral is used to corresponding part.The system of some embodiments of the present invention application drawing 3.Receiver 306 is preferably in the interior work of coverage of digital broadcast network (DBN) 300.Receiver 306 can receive the transmission that DBN300 provides.The transmission of DBN300 comprises transport stream (TS).DBN300 comprises the device of revising the transport stream that it is transmitting.DBN300 provides to produce and transmit has reference information formerly, for example pilot signal of describing in the example as Fig. 2 and the signal of data message.The pilot value that strengthens is included in the OFDM symbol, so be applicable.Receiver 306 receives the OFDM symbol that DBN300 transmits.Receiver 306 certainly can recognition data and formerly parameter information, for example pilot frequency carrier wave value.Receiver 306 also detects impulse disturbances.So receiver 306 can utilize the signal of reception and reference information formerly, pilot signal for example produces the estimator of the data value of representing primary signal.Advantageously, the user of receiver 306 does not need in advance such activity to be made amendment, and receiver 306 can be when receiving service, connects ground and substantially directly proofreaies and correct.Advantageously, receiver 306 does not need to be used to proofread and correct any reciprocation of the data value of representing primary signal.So the invention cost of imbody is low.

Still referring to Fig. 3, digital broadcast network (DBN) 300 sends data to user by data/communication link.The example of DBN300 is digital video broadcasting (DVB) or the ISDB-T that is configured to data information.Advantageously, use digital video broadcast-terrestrial (DVB-T) in the present invention.DBN300 comprises the ability that transmits data by data link.Before the transmission, deal with data in DBN300.

Well known in the art, IP wrapper 304 is carried out multi-protocols encapsulation (MPE), and the IP data are put into data capsule based on Motion Picture Experts Group-transport stream (MPEG-TS).The generation of wrapper 304 executive table, the link of form and the modification of form.On the other hand, the multiplexer of DBN300 can be realized these tasks.

According to some embodiment, the operation of IP wrapper 304 can relate to puts into the UDP grouping to the data that receive, and the UDP grouping is encapsulated in the IP grouping, and the IP grouping is encapsulated in again in the DVB grouping.In the normative document EN301 192 that is contained in this as a reference, can find the details of this multiprocol encapsulation over ATM.In application layer, available agreement comprises UHTTP (unidirectional HTTP), RTSP (real-time streaming agreement), RTP (RTP), SAD/SDP (service declaration protocol/services is described agreement) and FTP.

In further embodiments, the IP encapsulation can utilize IPSEC (internet protocol secure) to guarantee that content will be had the receiver use of appropriate voucher only.In encapsulation process, unique identifier can be added at least one head.For example, when using UHTTP, unique identifier can be encoded in the UHTTP head under the UUID field.So in certain embodiments, for the data of catering to particular terminal or one group of terminal transmit, container also can be held address information, and described address information can be received the conditional access component recognition in the device 306 and read, and whether is intended for this terminal with specified data.On the other hand, for the data of catering to a plurality of terminals transmit, can use multicast, advantageously, single transmitter can arrive a plurality of receivers.In the system of DNB300 and receiver 306, also can form VPN (virtual private network) (VPN).Certain bandwidth of the DBN300 that is broadcasting is assigned to from DBN300 to the receiver 306 point-to-point or point-to-multipoint delivery.DBN300 also can have the various transmission channels that are used for other stream that is moving.Receiver 306 is carried out the multi-protocols encapsulation, forms the IP packet.

Known in the art, the DVB grouping that produces like this transmits by the DVB data link.Receiver 306 receiving digital broadcast datas.Receiver 306 receives reference information formerly, pilot signal for example, and can proofread and correct the data value of the signal that is influenced by impulse disturbances.Receiver provides the simpler broadcast data with less delayed to receive.So receiver 306 can fully receive data, services, the user can utilize receiver 306 that the service that provides is provided.When transmission rate was stipulated by type conversion program (caster), this speed was observed.

Below, for some embodiments of the present invention provide the theoretical background details.

The front has illustrated Fig. 4.Below, corresponding Reference numeral is used to corresponding part.The example of Fig. 4 illustrates the generation as the blanking signal of the summation of the original of blanking sample and reverse side.Some embodiment main thought behind is by those impaired samples of the essence of deletion suspection at least, avoids the adverse effect of impulsive noise.These samples are by given value, and for example 0 replaces.Thereby, because distortion is being known format and rule, thus receiver FFT quite reliable after, can estimate the distortion that signal is caused.Certainly, the sample of deletion is also not exclusively known, but the signal after the blanking can be described as whole symbol time T _UThe transmitting and blanking time T of needs (but whether reliably known) _BDo not need the part summation.Time T _BThe required sample opposite (as shown in the example of Fig. 4) in sample and the identical time interval.

Referring to the example of Fig. 4, receiver carries out the FFT of blanking signal (a).When FFT was linear operation, it can be divided into two parts: the summation of the FFT of desired signal (b) and opposite sample (c).(it can be according to previous OFDM symbol because desired signal comprises known pilot value, also can estimate in some cases) according to OFDM symbol after a while, therefore can estimate the contribution of blanking sample according to pilot value with respect to the departing from of the desired value that does not have blanking.The mode of desirable in theory this operation of execution is when providing pilot value and depart from, and according to the Minimum Mean Square Error estimator, estimates that carrier wave departs from.Best, the knowledge of the deviation value by only utilizing two (perhaps maximum four) immediate pilot signals can obtain very satisfied performance simply.For the performance of the best, the information that can use all pilot value obtains each carrier wave and departs from estimator on the other hand.

Some embodiments of the present invention are used a plurality of pilot signals, the following describes the theoretical details about it.General embodiment for obtaining goodish estimator can use orthogonality principle and obtain appropriate weight w _j, pilot tone departs from p _jShould be multiplied by this weight w _j, so that find out the linear MSE estimator b that carrier wave departs from (perhaps corrected value) _kThis principle can be write as a prescription formula:

$E\left\{(b_k-\underset{j}{\mathrm{\Σ}}{w}_j{p}_j)p_l^{*}\right\}=0\∀l,l=0,m,2m...---\left(1\right)$

Wherein k is a carrier index, and * represents complex conjugate, and m is pilot interval (for DVB-T, in an OFDM symbol, m is 12), and E{} represents to add up the computing of averaging.For each carrier index, this can be write as:

$c_b(k,l)={\underset{\‾}{c}}_p^T\left(l\right)\underset{\‾}{w},l=0,m,...---\left(2\right)$

C wherein _b(k is to have k the covariance that carrier wave departs from that the pilot tone of index l departs from l).Certainly, index l is effective pilot tone index from this group carrier index acquisition value thereby have only each m value.Covariance c _b(k l) is calculated as

$c_b(k,l)=E\{b_k\·p_l^{*}\}.---\left(3\right)$

Similarly, vector c _p(l) comprise pilot tone and depart from covariance (subscript T representing matrix transposition) afterwards.These vectors have with general case under the as many element of pilot signal.Vector c _p

(l) i element provided by following formula:

c _p(l) _i＝c _p(im-l) (4)

The covariance c of right-hand side _p(δ) be defined by

$c_p\left(\mathrm{\δ}\right)=E\{p_j\·p_{j-\mathrm{\δ}}^{*}\}.---\left(5\right)$

Top illustration formula supposition departs from can be counted as broad sense steady-state process (result of (5) and pilot tone index j are irrelevant), and for actual signal, this is a reasonably supposition.

Can be advanced further a step, and employing is comprised all pilot tone index l=0, m ... (M-1) matrix notation of m is write as

${\underset{\‾}{c}}_b\left(k\right)={\underset{=}{C}}_p\underset{\‾}{w}---\left(6\right)$

Here vector c _bWith wIn the number of element identical with the number (M) of pilot tone.

The vector of left-hand side c _b(k) provide by following formula

${\underset{\‾}{c}}_b\left(k\right)=\left[\begin{array}{c}{c}_b(k,0)\\ c_b(k,m)\\ c_b(k,2m)\\ .\\ .\\ c_b(k,(M-1)m)\end{array}\right]---\left(7\right)$

And matrix C _PIt is (the covariance matrix of M * M) that departs from by the pilot tone that following formula provides

${\underset{=}{C}}_p=\left[\begin{array}{ccccc}{c}_p\left(0\right)& c_p\left(m\right)& c_p\left(2m\right)& .& c_p\left((M-1)m\right)\\ c_p{\left(m\right)}^{*}& c_p\left(0\right)& & & \\ c_p{\left(2m\right)}^{*}& & .& & \\ .& & & .& \\ c_p{\left((M-1)m\right)}^{*}& & & & c_p\left(0\right)\end{array}\right].---\left(8\right)$

$\underset{\‾}{w}={\left({\underset{=}{C}}_p\right)}^{-1}{\underset{\‾}{c}}_b\left(k\right).---\left(9\right)$

Utilize matrix inversion now, can formally find the solution required weighted value w, as follows

Subsequently, the carrier wave corrected value b of k carrier wave _kBe estimated as

Vector wherein PComprise the pilot tone deviation value

b _k＝ w ^T P， (10)

P＝[p ₀?p _m..p _(M-1)m] ^T. (11)

From the carrier value of the FFT of the sample of signal that comes from blanking, deduct these corrected values b _k

Some embodiments of the present invention are used two pilot signals, the following describes the theoretical details of these embodiment.For some the simplest realizations, if use a large amount of pilot signals, so in some cases, matrix inversion is trouble, and other set of equations solution technique also is like this.But, even application pilot signal seldom also can access good estimator.The simple case of only using two immediate pilot signals especially provides goodish performance in DVT-T in many systems.

Referring to the embodiment of simple two pilot signals, estimate only to utilize k carrier wave of immediate pilot signal to depart from.This can utilize equation (10) and (9) to realize.Weight vectors wTo only have two element w ₀And w ₁Utilize (9) to calculate wValue.Below, write out two matrixes of equation (9) right-hand side.

Index less than the pilot frequency carrier wave of k should be that (k, m), (k m) means k mould m to mod to k-mod here.The index that is higher than the pilot frequency carrier wave of k should be k-mod (k, m)+m.Now in (9) C _pMatrix is 2 * 2 matrixes as follows

${\underset{=}{C}}_p=\left[\begin{array}{cc}{c}_p\left(0\right)& c_p\left(m\right)\\ c_p{\left(m\right)}^{*}& c_p\left(0\right)\end{array}\right]---\left(12\right)$

It and k have nothing to do.Can easily calculate required matrix inversion in (9) about each blanking interval length in advance.Covariance c _p(m) depend on this length (and shape of blanking window).The covariance vector c _b(k) can be write as

${\underset{\‾}{c}}_b\left(k\right)=\left[\begin{array}{c}{c}_b(k,k-\mathrm{mod}(k,m))\\ c_b(k,k-\mathrm{mod}(k,m)+m)\end{array}\right]---\left(13\right)$

Wherein only use two immediate pilot signals.If considered to depart from the broad sense stable state essence of process, the deducibility covariance function only depends on the difference of index (carrier wave and pilot tone).Thereby (13) are simplified to

${\underset{\‾}{c}}_b\left(k\right)=\left[\begin{array}{c}{c}_b\left(\mathrm{mod}(k,m)\right)\\ c_b(\mathrm{mod}(k,m)-m)\end{array}\right].---\left(14\right)$

Vector c _b(k) only has (at most) m-1 to possible complex values, because do not need the estimating pilot frequency value.Otherwise modulo operation means that each repeats one group of identical power to the pilot tone index to other

$b_r=\frac{1}{N}\underset{k=0}{\overset{N-1}{\mathrm{\&Sigma;}}}{c}_k\underset{q=l_o}{\overset{l_o+\mathrm{<figure-callout\; id="2"\; label="L\; e\; j"\; filenames="H028291840E00081.png"\; state="\{\{state\}\}">L</figure-callout>}}{\mathrm{\&Sigma;}}}{e}^j{2\mathrm{\&pi;q}\frac{k^{\&prime;}-r}{N}}^{}.---\left(18\right)$

Heavy.For example, for DVB-T, this means that 11 groups of complex values are right.This is the very reasonably number that will have in the memory.Because strong symmetric cause, it only is half of the upper limit that this value still trends towards.Owing to can know signal properties and blanking window in advance, therefore can calculate weight vectors about m-1 carrier index w, and it is stored in the memory.

For the final carrier wave corrected value b that estimates (10) _k, we also need pilot vector as follows

$\underset{\&OverBar;}{P}=\left[\begin{array}{c}{p}_{k-\mathrm{mod}(k,m)}\\ p_{k-\mathrm{mod}(k,m)+m}\end{array}\right].---\left(15\right)$

Some embodiment of estimation routine described above need depart from the knowledge of the covariance of process.The method that obtains these knowledge has several.At first, can consider modulation parameter, under the situation of length of window and shaping, obtain theoretical covariance function.If carry out some approximate and simplification hypothesis, this can be feasible at least.Second method is the computer simulation of operation about required system parameters, thereby obtains the reliable estimator of covariance value.This can provide good result quite simply.The third method can be based on measuring some prototype receivers, thereby obtain covariance value.The 4th kind of method is about covariance function, takes some rational smoothed approximations.This time best method causes quite simply realizing.

As an illustration example, we derive the auto-correlation function that departs from process about DVB-T formula signal.As what illustrate in the DVB-T standard, we suppose that real number signal s (t) is provided by following formula

$s\left(t\right)=\mathrm{Re}\left\{e^{j{\mathrm{\&omega;}}_{c}t}\underset{k=0}{\overset{N-1}{\mathrm{\&Sigma;}}}{c}_{\mathrm{<figure-callout\; id="2"\; label="k\; e\; j"\; filenames="H028291840E00081.png"\; state="\{\{state\}\}">k</figure-callout>}}{e}^j{2\mathrm{\&pi;}{k}^{\&prime;}\frac{1}{T_U}}^{}\right\}---\left(16\right)$

Here ω _cBe the central angle frequency, k '=k-N/2, c _kBe the complex coefficient that is positioned at the carrier index k of the modulated position of expression, T _UIt is the duration of useful OFDM symbol (unguarded interval).The FFT scale of the OFDM modulation that N is to use.Below, we use the complex envelope symbol, and calculate l the sample that obtains every time T, T=T here _U/ N, as follows

$s_t=\underset{k=0}{\overset{N-1}{\mathrm{\&Sigma;}}}{c}_{\mathrm{<figure-callout\; id="2"\; label="k\; e\; j"\; filenames="H028291840E00081.png"\; state="\{\{state\}\}">k</figure-callout>}}{e}^j{2\mathrm{\&pi;}{k}^{\&prime;}\frac{1}{N}}^{}.---\left(17\right)$

In order to determine to depart from the auto-correlation function of process, we at first calculate at interval [l ₀, l ₀+ L) in, sample s _lDiscrete Fourier transform (DFT) (Fig. 4 (c)).The value that is positioned at carrier index r is calculated as

Can obtain the autocorrelation that carrier wave departs from now is about

$c(r,s)=E\left\{b_r{b}_s^{*}\right\}\&cong;\frac{1}{{\mathrm{<figure-callout\; id="2"\; label="N"\; filenames="H028291840E00081.png"\; state="\{\{state\}\}">N</figure-callout>}}^2}\underset{k=0}{\overset{N-1}{\mathrm{\&Sigma;}}}E\left\{{\left|c_k\right|}^2\right\}\underset{q=l_o}{\overset{l_o+\mathrm{<figure-callout\; id="2"\; label="L\; e\; j"\; filenames="H028291840E00081.png"\; state="\{\{state\}\}">L</figure-callout>}}{\mathrm{\&Sigma;}}}{e}^j{2\mathrm{\&pi;q}\frac{s-r}{N}}^{}.---\left(19\right)$

In deriving example, suppose modulation value c _kBe zero mean, and statistics is upward independent, and the blanking length L is less, for example less than 10% of whole symbol period (N sample).Be also noted that for DVB-T some c _kValue is 0, so that in fact, and outside summation is from 0 to n-1, and n is the number of effective carrier wave here.(19) autocorrelation has c really, and (r, value s) only depends on the required character of the difference (s-r) between index value s and the r.Now, for noise-free case, required covariance is directly provided by top equation.If have noise (and considering best mode), tackle the pilot tone covariance matrix so C _PMake slight change.Thereby, replace (12) resulting matrix to be written as [ignore accurately and depart from, be simple]

${\underset{=}{C}}_p=\left[\begin{array}{cc}{c}_p\left(0\right)+{\mathrm{\&sigma;}}^2& c_p\left(m\right)\\ c_p{\left(m\right)}^{*}& c_p\left(0\right)+{\mathrm{\&sigma;}}^2\end{array}\right]---\left(20\right)$

Here σ ²It is noise variance.

Some embodiments of the present invention are used time good being similar to.For many actual realizations, use correlation function c (r, s) or the good approximation of c (f) just enough.Here variable f is relative frequency difference (r-s).If the blanking window in the time domain quite low (and symmetry), and be positioned at OFDM symbol end near, the frequency domain correlation function is quite broad so, this function not can 0 and m between too much change, m is two difference on the frequencies (difference of pilot tone index) between the continuous pilot signal here.In addition, can suppose that the linear change in the correlation function availability interval [0, m] is similar to.Normalized correlation function is taked following this form

$c\left(f\right)=\left(\frac{\mathrm{\&rho;}-1}{m}\right|f|+1)e^{j\frac{\mathrm{\&theta;}}{m}f}---\left(21\right)$

Here ρ is the value of the coefficient correlation under difference on the frequency m, and θ is a corresponding phase.If the center of blanking window is set at 0 sample (blanking is carried out at the two ends at this symbol symmetrically), θ is 0 so, otherwise it is less number.Now, calculate carrier wave corrected value b according to (10) _kIn required covariance matrix C _PProvide ((21) substitution (12)) by following formula

${\underset{=}{C}}_p=\left[\begin{array}{cc}1& \mathrm{\&rho;}{e}^{\mathrm{j\&theta;}}\\ \mathrm{\&rho;}{e}^{-\mathrm{j\&theta;}}& 1\end{array}\right]---\left(22\right)$

The covariance vector c _b(k) can be rewritten into (rewrite from (14), and do not consider thermal noise)

${\underset{\&OverBar;}{c}}_b\left(k\right)=\left[\begin{array}{c}\left(\frac{\mathrm{\&rho;}-1}{m}\right|\mathrm{mod}(k,m)|+1)e^{j\frac{\mathrm{\&theta;}}{m}\mathrm{mod}(k,m)}\\ \left(\frac{\mathrm{\&rho;}-1}{m}\right|\mathrm{mod}(k,m)-m|+1)e^{j\frac{\mathrm{\&theta;}}{m}[\mathrm{mod}(k,m)-m]}\end{array}\right].---\left(23\right)$

Now, weight vectors (9) can be rewritten into (utilizing (22) and (23))

$\left[\begin{array}{c}{w}_0\\ w_1\end{array}\right]=\left[\begin{array}{c}{e}^{\mathrm{j\&theta;}\frac{\mathrm{mod}(k,m)}{m}}(1-\frac{\mathrm{mod}(k,m)}{m})\\ \frac{\mathrm{mod}(k,m)}{m}{e}^{-\mathrm{j\&theta;}+\mathrm{j\&theta;}\frac{\mathrm{mod}(k,m)}{m}}\end{array}\right].---\left(24\right)$

This result is simple, and has the favourable character that actual correlation ρ has been calculated.Thereby under quite general supposition, weighting (24) is sane and effective.Mainly, only require with total OFDM symbol lengths and compare, blanking window short (and symmetry), and be located substantially on the symbol afterbody.For some embodiment, this brings receiver not need according to blanking length adjustment weight-the only require favourable character of position of window (central point).

Value θ depends on the blanking position of window.If the input sample vector after the receiver displacement blanking, so that the blanking window is symmetrically located at the starting point and the terminal point (that is, blanking window center point is 0) of resulting vector, is worth θ so and can becomes 0.This has further simplified the calculating in (24), and causes the desirable realization among some embodiment.But this best method also requires the linear phase shift that causes with the displacement of the sample in the time domain, proofreaies and correct the carrier value of having proofreaied and correct again.Whether this time good scheme is feasible, depends on actual chip architecture, and it is more suitable perhaps need to understand about the method (utilizing equation (12) and (14)) of more a little knowledge of correlation function.

Avoid the sample that in time domain, is shifted if desired, utilize the phasing in the frequency domain so, can obtain identical effect.(21) correlation function becomes following form

$c\left(f\right)=\left(\frac{\mathrm{\&rho;}-1}{m}\right|f|+1)e^{j\frac{\mathrm{\&theta;}}{m}f}\&CenterDot;{\mathrm{<figure-callout\; id="2"\; label="e\; j"\; filenames="H028291840E00081.png"\; state="\{\{state\}\}">e</figure-callout>}}^j---\left(25\right)$

Here i is the window's position displacement (number with sample is represented) in the time domain.The formula of back (22)-(24) correspondingly change.

Replace (21), can use and the corresponding actual correlation function of blanking window, and be similar in (25), carry out phasing according to the actual window position at zero position (perhaps near zero end).Advantageously, the blanking length of window can quite be grown (for example in the 2k system about 100), thereby, blanking the window's position that a treating number is quite little (for example, about 20-30 in 2k DVB-T).For system,, approximately there be m/2 the phase correcting value (remaining phase correcting value simple correlation) that will calculate for each the window's position with pilot interval m.Consider and also can utilize simple relation to handle the window's position of half that the result is that B is the number that covers the required blanking window of whole OFDM symbol as long as store (perhaps calculating fully) approximately Bm/4 complex phase bit correction value here.For having the DVB-T at the 2k of preceding number, this is about 60 plural numbers, and advantageously, this is (and by selecting parameter rightly, the part of these values is overlapping, this has further reduced required memory/disposal ability) quite reasonably in a small amount.

The front has illustrated Fig. 5 and 6.Below, corresponding Reference numeral is used to corresponding part.Fig. 5 and 6 example be in the mode of less delayed, reduces and tolerate ofdm system based on pilot signal, especially utilizes the pulse train noise in the ofdm system of DVB-T standard.Fig. 5 and 6 example adopt two immediate pilot signals to estimate the carrier wave corrected value.The signal that receives is carried out mould-number (A/D) conversion (square frame 500), and the sample of received signal is processed.Before A/D or in any convenient stage afterwards, can exist IQ-to separate.Fig. 5 and 6 example adopt the complex signal symbol everywhere, and are general on this meaning.Best, real number and imaginary part are used in actual realization respectively.

In step 600, detect the existence of impulsive noise.This can comprise the detection of impulse level or power.The pulse train noise measuring can in the method, be calculated the power of the sample of some based on the sliding window computational methods.Described number should be less, probably between 5 and 18 (in DVB-T, 8 samples are about 1 microsecond).If with the difference of reference value greater than threshold value, determine to exist impulsive noise so.Also can use other method.

In step 602, blanking is subjected to the sample of pulse influence.Best, the length of blanking interval should equal burst length, has only not surpass for the maximum length of recovering to get final product.Also can use the selection of predetermined blanking length, in other embodiments, only use a length.Best, can adopt the constant length-specific window of diverse location to cause one of simple realization.Can change (square frame 502) in serial parallel and carry out blanking before.Best, in input buffer (IB) (square frame 503), carry out blanking by control device (square frame 508) control.Control device (square frame 508) also keeps the record about the affected samples index.The blanking window can be simple rectangular window.On the other hand, the blanking window can have a certain shaping, for example linearity or cosine square ending transition (ending transition).

In step 604, calculate first estimator of received signal.Calculating has the fast Fourier transform (FFT) (square frame 504) of the signal of blanking, and transmits it (square frame 505), and result of calculation is stored in the output buffer (OB) (square frame 506).In this stage, obtain the first distortion estimator that transmits.Because will there be some distortions in the cause of blanking.The value of pilot frequency carrier wave is not the pilot transmitted carrier wave, but the value of the pilot frequency carrier wave of distortion.But, correct pilot value is known, receive (on the meaning of channel estimating) as long as formerly the symbol quilt is correct arbitrarily, and a symbol is between another symbol, channel variation is not too big, so that can produce first estimator of channel status according to history quite reliably.This is the very reasonably hypothesis for fixing and portable reception, and for the displacement situation, effective too.Known pilot value also can be result's (pilot value of collecting from several continuous OFDM symbols) of more complicated time domain interpolation.

In step 606, the difference between calculating observation value and the known actual value.In summing unit (square frame 509), the difference between the known actual value (square frame 510) of calculating observation pilot value (square frame 511) and pilot frequency carrier wave.For pilot signal, these given values are the transmission pilot value that multiply by the channel estimating amount under the pilot carrier frequency.

In step 608, calculate weighted value (w).In square frame (square frame 512), calculate and blanking the window's position the weighted value (w) that the modulation of length and application (equation (9) among for example general embodiment) is corresponding.Obtain information from control unit (square frame 508) about the blanking position of window.Best, a carrier value estimates to use two pilot signals.But the phasing instrument of one of simple embodiment applicable equations (24) is determined weighting (w), both needn't know length of window, needn't know modulation parameter again.But calculated in advance weighted value (w) is also read from memory.Advantageously, consequential pilot tone between the identical one group of weighted value (w) of repeated application, thereby required memory is quite little.

In step 610, calculate the carrier wave corrected value of each carrier wave.Calculate the wanted carrier corrected value (b of each carrier wave (may except pilot signal) at square frame (513) _k).These computing application equation (10) and (15).

In step 612, the estimator after the correction of calculating emission symbol.By from what step 404, produce, be stored in and deduct corrected value (square frame 512) in the estimator in the output buffer (OB) (square frame 506), the estimator after the correction of calculating emission symbol.The carrier value of proofreading and correct is forwarded, so that use.So, under the situation that tolerance is disturbed, can fully receive data, services.

Alternative among Fig. 5 comprises frame of broken lines (square frame 515).In alternative, be the mode at center always making the blanking window with zero sample, displacement (rotation) input sample in input buffer (IB) (square frame 503).Weighted calculation (square frame 512) is identical all the time, and this is simple, so useful.In addition, according to the displacement of the blanking window of reality, receiver each the carrier wave compensating phase shift (in square frame 515) of having nothing for it but.This alternative has essentially identical complexity.

Some embodiment of each square frame of Fig. 5 can be divided into four parts in fact: the detection of pulse train (position and length), and by the blanking of blanking sample and FFT, the correction of first estimator of the estimation of carrier wave corrected value and receiving symbol.

Some embodiments of the present invention have been used the detection of pulse train.Detect for pulse train, have several possibilities (some are learned previously) from document.Preferable methods is to utilize the sliding window method, in the method, monitors the power of instantaneous reception, and compares with a certain reference value.Described reference value can be, for example the average power of symbol (signal level keeps identical level substantially, so that measure can be to be like this for fixing or portable reception quite reliably-at least) formerly.Reference value also can be a certain previous length of delay of sliding window power calculation.Other possibility means that are used for the pulse train detection be to monitor surpassing of a certain amplitude threshold.In addition, when this method of application, windowhood method can be useful.Criterion can be that the level of some is intersected in this window, and all samples that belong to window can be marked as " under pulse train ".Another kind method can be to monitor changes in amplitude.Can calculate the difference of two continuous samples, obtain absolute value, and with threshold ratio.Equally, in the method, windowhood method also is useful, if surpass threshold value variation outnumber a certain limit number, can determine the existence of pulse train so.Also there is other possible method, for example the combination of said method.

Some embodiments of the present invention are used blanking.Use for blanking, also have several possibilities.A kind of simple method is only to use burst location information and constant blanking time.In addition, can from limited predetermined set, obtain blanking the window's position.Described position is selected to so that blanking interval is overlapped, and can handle the pulse train that is positioned at the optional position at least, as long as they are shorter than the length of lap.The limited selection of blanking length of window helps to reduce memory required in the weighted calculation.Handle a kind of more complicated of blanking, more effective mode is based on not only utilizes positional information but also utilize duration information.Those samples that belong to the detection window that satisfies the pulse train standard can be by blanking.Weighted calculation is used and blanking the window's position and the relevant information of length thereof now.For many possibilities, when needing weighted value, utilize program to calculate described weighted value at every turn.The shape of blanking window can be simple rectangle.On the other hand, also can be applicable to afterbody and have the shaping blanking window that seamlessly transits.The distortion that this window causes is less, is useful in some implementations.

Some embodiments of the present invention are used the estimation of carrier wave corrected value.For the estimation of carrier wave corrected value, also there are several possible methods.One of prevailing method is used all Given informations, i.e. pilot value and retainer belt value (perhaps pilot value adds those boundary belt values that belong to pilot tone grating (raster) m at least).Utilize all this available information formerly, can calculate each carrier wave and proofread and correct.As mentioned above, this can cause performance to improve some very little complicated realizations.Another kind method is only to use two immediate pilot signals to estimate the carrier value correction.In the present embodiment, can use actual covariance function (calculating, simulation or measure; Even can comprise that " in transmission " derive the measurement mechanism of covariance function, but this measurement mechanism can be set up more complicated method), perhaps aforesaid method for simplifying can use in addition that to be different from approximate other of the simple linear that provides herein approximate.Just derive covariance function, there are two possible main policies: 1) make the blanking window remain on its home position, derive covariance function considering under the situation of physical location, 2) by displacement/rotation input sample, so that the blanking window is center (perhaps fixed position in its vicinity) with zero all the time, adopts another kind of method.In one embodiment of back, before continuing to enter in the receiver, each carrier value needs independently phasing (square frame 515 in the example of Fig. 5).

Some embodiments of the present invention are used the correction of first estimator.The main mode that realizes the correction of first estimator is: the corrected value that deducts estimation from correspondence first estimator of carrier wave.But, whether being rotated according to input buffer (IB) (503), the carrier value after the correction may need phasing.

On the chip on the acceptor device, realize the preferred embodiments of the present invention.For example, the present invention is included in the DVB-T chip on the acceptor device.On the other hand, the present invention can be used in the middle device of intervening data traffic in the broadcast system, for example the gateway of the communication between at least two different network interfaces of bridge joint.Some embodiments of the present invention are supported the portable reception in the IP data broadcast receiver, and may be able to work under exacting terms.Thereby the performance of embodiment has promoted advantage of the present invention, for example economy.For example, DVB-T provides the mode of effective cheapness of distribute data, even under harsh or noisy condition, embodiment also can promote the low delay of broadcast data stream, simpler reception.

The front has been described Fig. 7.Below, corresponding Reference numeral is used to corresponding part.The example of Fig. 7 has been described the functional-block diagram of receiver.The receiver 306 of Fig. 7 can be used in Fig. 4,5 and 6 the examples arbitrarily/all.Receiver 306 comprises processing unit CPU703, multi-carrier signal receiver part 705 and user interface UI (701,702).Multi-carrier signal receiver part 705 and user interface UI (701,702) and processing unit CPU 703 couple.User interface UI (701,702) comprises display and the keyboard that makes the user can use receiver 306.In addition, user interface UI (701,702) comprises the microphone and the loud speaker of reception and reproducing audio signal.User interface UI (701,702) also can comprise the speech recognition (not shown).Processing unit 703 comprises the microprocessor (not shown), and memory 704 may also have software SW (not shown).Software SW can be stored in the memory 704.Microprocessor is according to software SW, the operation of controlling receiver 306, and for example reception of data flow, in the Data Receiving, the tolerance of pulse train noise, the reading of output in the explicit user interface and the input that receives from user interface UI.In the example of Fig. 5 and 6, certain operations has been described.For example, the hardware (not shown) comprises the device of detection signal, demodulating equipment, detect the device of pulse, blanking exist a large amount of impulsive noises symbol those samples device and calculate the device of estimator, the device of the correction of the device of acquisition weight and carrier wave corrected value and execution damaged data.

Still referring to Fig. 7, on the other hand, can application firmware or software realize (not shown).Receiver 306 can be the handheld apparatus that the user can cosily carry.Advantageously, receiver 306 can be the cellular mobile telephone machine, and described cellular mobile telephone machine comprises the multi-carrier signal receiver part 705 that receives broadcast transmission stream.So, receiver 306 can with service provider's reciprocation.

Fig. 8 has represented the example about the result of the ofdm signal with 2048 carrier waves, wherein according to another embodiment of the present invention, has proved that the impulse disturbances of less delay reduces.Thereby, proved that the potential of this method, described ofdm signal have at interval 12 pilot signal and from effective carrier wave of 0-1704 with the example with 2048 ofdm signals.Utilized carrier wave to produce test signal with random phase and amplitude.The amplitude of " data carrier " is limited, so that pilot power is 16/9 times of maximum power of data carrier.The sample of signal that produces in time domain by blanking (having) from 125 samples of the index of 292-417.The primary signal of the no blanking of curve 800 representatives.Dotted line 802 representatives have the received spectrum of blanking.Represented primary signal and the blanking signal in the frequency domain among Fig. 8.Utilize the curve (804) of zone circle to provide according to correction result of the present invention.Pilot signal is positioned at index 732,744 and 756.For the sake of clarity, only presented a part of frequency spectrum.In addition, Fig. 8 has also described according to this routine decoded signal.Can notice that also carrier amplitude is mated with the present invention better at least.

Fig. 9 has represented from the example of the mean square deviation of the carrier wave of 0-500, wherein according to another embodiment of the present invention, has proved that the impulse disturbances of less delay reduces.The squared absolute value of the difference of the original value of mean square deviation application reception carrier complex values and each carrier wave.Fig. 9 has described these mean square deviations of preceding 500 carrier waves.Curve 900 representatives only have the result of blanking.Curve 902 representatives are according to correction result of the present invention.Can conclude and aspect error power, have about 10 times difference at least.In fact, in whole OFDM symbol, the power difference of the calculating of this example of acquisition [=with only carry out blanking and compare, the improvement that is caused by the present invention] is 16.4dB, and the residual error power of correction signal is-28.5dB that this should provide the connection of high-quality.

Best, the invention provides the pulse train that quite simple device reduces high level, need only in the sample, their length less than or identical with the number of pilot frequency carrier wave in the ofdm signal basically.For example, for the 8k system, burst length is about 100 microseconds, and for the 2k system, burst length is about 25 pettiness.For such length, performance can be restored at least the level applicable to the most sane modulating mode.For shorter pulse train, even can adopt more responsive pattern.

Specific implementation of the present invention and embodiment have been described above.To one skilled in the art, the present invention obviously is not limited to the details of the embodiment that provides above, on the contrary, under the situation that does not break away from feature of the present invention, can realize the present invention in utilization is equal to other embodiment of means.Scope of the present invention is only limited by additional claim.

Claims (42)

1. method that is used to receive multi-carrier signal, described method comprises the steps:

Detect the existence of at least one impulse disturbances in the described signal,

Under the situation that has a large amount of impulsive noises that cause by described at least one impulse disturbances, the blanking sample, thus acquisition has the signal of blanking,

Determine described estimator with signal of blanking,

Determine the carrier wave corrected value, wherein said carrier wave corrected value depart from based on some carrier value of comparing with Given information and described blanking and

Utilize described carrier wave corrected value to influence estimator, thereby obtain the reproduction of desired signal.

2. in accordance with the method for claim 1, the step of wherein said definite estimator comprises: utilize described time domain-frequency domain transform with signal of blanking to calculate described estimator, and temporarily store described estimator.

3. in accordance with the method for claim 1, the step of wherein said definite carrier wave corrected value comprises the steps:

Difference between the pilot value of calculating observation and the given value of pilot frequency carrier wave, wherein the given value of pilot frequency carrier wave comprises described Given information,

Calculate and blanking position and the applied corresponding weighted value of system based on pilot tone,

According to the described difference and the described weighted value of each carrier wave, calculate the carrier wave corrected value.

4. according to the described method of aforementioned any claim, also be included in before the step of described definite estimator, so that the blanking window is the mode at the center sampled signal that is shifted with first sample position substantially, and before the estimated signal of transmitting after proofreading and correct, compensate the step of the phase shift of each carrier wave.

5. according to any one described method in the claim 1 to 3, wherein said detection step is based on the calculating of sliding window.

6. according to any one described method in the claim 1 to 3, wherein said detection step is based on monitoring the threshold value that surpasses signal amplitude.

7. according to any one described method in the claim 1 to 3, wherein said detection step is based on the variation of the amplitude of supervision.

8. according to any one described method in the claim 1 to 3, wherein said blanking step comprise blanking basically with the digital value of the corresponding to predetermined quantity of impulse disturbances.

9. according to any one described method in the claim 1 to 3, the described blanking step in its Shen comprises one group of predetermined blanking the window's position.

10. according to any one described method in the claim 1 to 3, wherein said blanking step comprises blanking and the corresponding to digital value of impulse disturbances.

11. according to any one described method in the claim 1 to 3, wherein said blanking step is based on the position of impulse disturbances and the application of duration.

12. according to any one described method in the claim 1 to 3, wherein said blanking step comprises that blanking directly is subjected to digital value that described impulse disturbances influences and the digital value adjacent with impulse disturbances.

13. according to any one described method in the claim 1 to 3, wherein the blanking window comprise rectangle blanking window and have the blanking window that seamlessly transits at afterbody at least one.

14.,, calculate the carrier wave corrected value wherein for different carrier based on different pilot value according to any one described method in the claim 1 to 3.

15., wherein calculate the carrier wave corrected value according to two immediate pilot tones according to any one described method in the claim 1 to 3.

16. in accordance with the method for claim 15, wherein in the calculating of carrier wave corrected value, use covariance function.

17. in accordance with the method for claim 16, wherein when deriving described covariance function, consider the blanking position of window.

18. in accordance with the method for claim 16, be the mode at center basically with first sample wherein according to making the blanking position of window, displacement input sample.

19. according to any one described method in the claim 1 to 3, wherein said some carrier value comprises the observation pilot frequency carrier wave value that is subjected to the received signal that described impulse disturbances influences.

20. according to any one described method in the claim 1 to 3, wherein said Given information comprises the pilot frequency carrier wave value that formerly receives.

21. in accordance with the method for claim 20, the wherein said pilot frequency carrier wave value that formerly receives comprises the transmission pilot value of the channel estimating amount that multiply by on the pilot carrier frequency.

22. in accordance with the method for claim 21, the wherein said pilot frequency carrier wave value that formerly receives is not subjected to the influence of impulse disturbances.

23. according to any one described method in the claim 1 to 3, wherein said Given information comprises the pilot frequency carrier wave value of interpolation, the pilot frequency carrier wave value of wherein said interpolation obtains from the OFDM symbol of a group of received, wherein is subjected to some pilot frequency carrier wave value that impulse disturbances influences according to before described some pilot frequency carrier wave value and the pilot frequency carrier wave value that receives afterwards and by interpolation.

24. in accordance with the method for claim 23, wherein said pilot frequency carrier wave value is multiplied with the in the channel estimating amount on the corresponding pilot carrier frequency.

25. the wherein said influence that is not subjected to impulse disturbances before with the pilot frequency carrier wave value that receives afterwards in accordance with the method for claim 24.

26., wherein at least one OFDM symbol of received signal, contain the pilot frequency carrier wave value according to any one described method in the claim 1 to 3.

27. according to any one described method in the claim 1 to 3, wherein said multi-carrier signal comprises ofdm signal.

28. in accordance with the method for claim 27, wherein said ofdm signal is exercisable in one of DVB system and ISDB-T system at least.

29. a receiver that is used to receive multi-carrier signal, described receiver comprises:

Be used to detect first circuit that at least one impulse disturbances exists in the described signal,

Be used under the situation that has a large amount of impulsive noises cause by described at least one impulse disturbances, the blanking sample, thus obtain to have the signal of blanking, and determine the second circuit of the estimator of described signal with blanking,

Be used for determining the tertiary circuit of carrier wave corrected value, wherein said carrier wave corrected value depart from based on some carrier value of comparing with Given information and described blanking and

Be used to utilize described carrier wave corrected value to influence described estimator, thereby obtain the 4th circuit of the reproduction of desired signal.

30. according to the described receiver of claim 29, wherein said multi-carrier signal comprises ofdm signal.

31. according to the described receiver of claim 30, wherein said ofdm signal is exercisable in one of DVB system and ISDB-T system at least.

32. according to the described receiver of claim 29, wherein said receiver also comprises and the interactive device of service provider that signal is provided.

33., wherein saidly be used for interactive device and comprise the honeycomb mobile module that in the coverage of cellular mobile network, to work according to the described receiver of claim 32.

34. according to the described receiver of claim 29, the wherein said second circuit that is used for determining estimator comprises the circuit of time domain-frequency domain transform of realizing described signal with blanking.

35. according to the described receiver of claim 34, the wherein said tertiary circuit that is used for definite carrier wave corrected value is configured to:

Difference between the pilot value of calculating observation and the given value of pilot frequency carrier wave, wherein the given value of pilot frequency carrier wave comprises described Given information,

Calculate and blanking position and the applied corresponding weighted value of system based on pilot tone,

According to the described difference and the described weighted value of each carrier wave, calculate the carrier wave corrected value.

36., comprise that also broadcasting the multi-carrier signal reception touches piece according to the described receiver of claim 29.

37. according to the described receiver of claim 29, wherein said receiver comprises the user terminal of at least one service that acquisition receives in signal.

38. a system that receives multi-carrier signal, described system comprises:

Be used to detect the device that at least one impulse disturbances exists in the described signal,

Be used under the situation that has a large amount of impulsive noises that cause by described at least one impulse disturbances, the blanking sample, thus acquisition has the device of the signal of blanking,

Be used for determining the device of the estimator of described signal with blanking,

Be used for determining the device of carrier wave corrected value, wherein said carrier wave corrected value depart from based on some carrier value of comparing with Given information and described blanking and

Be used to utilize described carrier wave corrected value to influence described estimator, thereby obtain the device of the reproduction of desired signal.

39. according to the described system of claim 38, wherein said system comprises at least one of DVB system and ISDB-T system.

40. a method that receives ofdm signal, described method comprises the steps:

Detect the existence of at least one pulse train,

Blanking is subjected to the sample of described at least one pulse train influence,

Calculate and describedly have, thereby obtain estimator by the time domain-frequency domain transform of the signal of blanking sample,

Difference between the pilot value of calculating observation and the given value of pilot frequency carrier wave,

Calculate and the corresponding to weighted value of blanking the window's position,

According to the described difference and the weighted value of each carrier wave, calculate the carrier wave corrected value and

From described estimator, deduct described carrier wave corrected value, obtain the reproduction of desired signal.

41., wherein calculate described weighted value according to following formula according to the described method of claim 40:

$\underset{\&OverBar;}{w}={\left({\underset{\&OverBar;}{\underset{\&OverBar;}{C}}}_p\right)}^{-1}{\underset{\&OverBar;}{c}}_b\left(k\right)$

Wherein w represents weighted value, C _pThe expression pilot tone departs from c _b(k) expression carrier index value.

42., wherein calculate described carrier wave corrected value according to following formula according to the described method of claim 40:

b _k＝ w ^T P，

B wherein _kExpression carrier wave corrected value, w represents weighted value, P represents the pilot tone deviation value.

Images